Electric furnace.



P. WRIGHT. ELECTRlC FURNACE. APPLICATION Flt-ED SEPT. 13. 1913.

PatentedSept. 7, 1915.

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APPLICATION FILED SEPT. I3. 1913- PatentedSept. 7, 1915.

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v siding at Vancouver,

PARVIN WRIGHT, OF SEATTLE, WASHINGTON.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Sept. 7, 1915.

Application filed September 13, 1913. Serial No. 789,724.

To all whom it may concern:

Be it known that I, PARVIN WRIGHT, a citizen of the United States, formerly rein the county of New Westminster, Province of British Columbia, and Dominion of Canada, but now residing in Seattle, in the county of King and State of Washington, haveinvented a new and useful Electric Furnace, of which the following is a specification.

The object of my invention is to provide an electric furnace suitable for smelting ores such as magnetite, chromite, hematite and other similar products of iron ore known as black sand, obtained in granulated form from beaches, streams, etc. As the magnetite or black oXid of iron is saved by a magnetic separator and conveyed to bins or tanks through a hydraulic flume where it is deposited along with latter overflows, leaving the magnetite clean and in a damp or wet condition. Therefore, it is necessary to dry the material before it gets to the melting zone of the furnace and one object of the present invention is to utilize the waste heat of the electric furnace in performing this drying operation.

Another object of the invention is to utilize a portion of the waste heat of the furnace in pre-heating the charge before "the ore comes into the smelting zone.

. Another object of the invention is to provide improved means for conducting the current to the smelting zone of the electric furnace, and in that connection one object of the invention is to provide an improved form of transformer for supplying current to the furnace.

Another object ofnmy invention is to construct a furnace so that the molten charge can be drawn ofi without tilting the furnace and without the use of a tap opening.

()ther objects of the invention will appear hereinafter.

The accompanying drawings illustrate embodiments of. my invention, and referring thereto:

Figure 1 is a horizontal section of the furnace. Fig. 2 is a section thereof on line m w Fig. 1. Fig. 3 is a section on line a2 w Fig. 2. Fig. 4 is a plan view of a modified form of transformer for supplying current tothe furnace. Fig. 5 is a vertical longitudinal section, partly in elevation of the secondary of such transformer. Fig. 6 is a transverse sectlon of the electrode thereof.

the water, the

formed with an internal chamber 2, the

lower portion of such chamber being lined with refractory material indicated at 3 to form a crucible 4, and the wall of the furnace body having an opening .5 at one side, the crucible lining 3 extending within this opening and over a lip 6 providing for discharge of the melted metal when required. Above the crucible provided with a chamber 7 and an ore feeding chute, stack or chamber 8 extends within the chamber 7 and is provided with a hopper or funnel 9 at its upper end for receiving the ore, said chute being open at its lower end as indicated at 10 for discharge of ore to the pre-heatingzone. The walls of the chute or chamber 8 are preferably of metal and are preferably bent or flanged 11 at their lower inwardly as indicated at or shoulders tendends to form obstructions ing to resist or retard the ment of. the ore. Additional obstructing means are preferably provided in the form of blades or prongs 12 extending inwardly from the lower ends of arms 13 on rock shafts 14 mounted to turn in bearings on the furnace body and provided with operating handles 15, whereby said blades 12 may be moved inwardly or outwardly, as required. Suitable means such as a plate 16 is provided for closing the chamber 13 at its top, said chamber serving to receive the hot gaseous products from the smelting and pre-heating zones and to retain the same around the chute or chamber 8 so as to communicate the heat thereof to the ore in said chamber. The walls of said chamber may be perforated as shown at 17 in Fig. 3 to permit the moisture or gases driven off from the ore to escape into the chamber 13 and permit gases in the chamber 13 to pass through said openings into the ore in the chute.

Suitable means and carbon chute such as an ore chute 18 19 are provided for supplying to the chute 8, the ore and the carbon for reducing the ore.

At opposite ends of the crucible 4 are provided electrodes 20 which are connected to the secondary member 21 of a-transformer. In order to provide for high .conductivity and at the same time provide a construction which is sufiiciently resistant to heat, I form the electrodes 20 as boxes downward moveand adjacent to the portion of the wrought.

'or hollow bodies of suitable heat resistant 24 being secured in the box electrodes 20 and communicating therewith, and the copper *being melted and poured into the hollow structure thus formed, so as to completely fill the same and form a secondary conductor composed of a copper core surrounded by a wrought iron shell throughout. In the operation of the furnace the portion of the copper core which is Within electrodes becomes melted, and the face iron shell between said copper and the metal in the bath also become melted and diflused into the cast iron in the bath and into the copper in the electrode. Owing to the cooling effect of the oil in the tube 27, the main body of copper in the electrode is kept below the melting point, the oil being generated into gas which passes out through the hollow head 29, and such generation of gas absorbing considerable heat. I have found hat by this means the temperature in the body of the electrode ,may be kept down to about 1500F. and that only a small amount of the electrode core is melted.

I desire to avoid water cooling which carries away and wastes the heat, but for certain grades of steel and for oxidizing, I provide means for supplying oil, gas or other material to the body of smelted metal in the crucible, such means, consisting for example, of a small wrought iron pipe 27 having a valve 27' and extending axially within the secondary conductor 21 adjacent to the electrodes and into a hollow cap or head 28 on the electrodes, said cap being of any suitable refractory material, for example, fire clay and being provided with a distributing chamber 29 and with discharge openings 30 through which the oil or gas is injected into the body of melted metal in the crucible.

The electrode conductor 21 is preferably U-shaped, forming a coil of a single turn wound or extended around a transformer core or cores 32. In using a single-phase current, a onepiece transformer core may be used, as is common in such devices, but in large furnaces it is desirable to use polyphase currents such as two-phase and threephase, and in such cases Ifind it preferable to use a transformer core having two branches 32, as shown in Fig. 1, or three branches as shown in Fig. 4, with a primary winding 33 on each branch and one secondary coil 21 common to all of the primary coils used, said primary windings being connected so that one of said windings is reversed relatively to the other so as to produce a resultant electromotive force in the secondary coil. The sides or parts of the several cores which are within the secondary winding are arranged close together, but the cores diverge so that their other sides, extending through the primary windings, are separated to provide room for the separate windings. That portion of the secondary circuit which passes around the transformer core or cores 32 may be made of sheet copper with slight circulating spaces between them, but is preferably constructed of Wrought iron pipe 24 as stated, filled with copper. By forming this wrought iron pipe of sections fitted together with the usual elbow fittings indicated at 24, the secondary conductor may be brought very close to the core, so as to cut all the lines of force and prevent loss.

The operation is as follows: The ore is fed into the hopper 9 from the chute 18, and carbon is supplied from chute 19, and the charge descends through the chute or chamber 8 into the crucible 4. Electric current being passed between the electrodes, causes the ore and carbon to be heated to a high temperature with the result that the ore is smelted and the melted metal collects in the crucible while the gaseous products of the smelting operation rise and collect in the chamber 13 and heat the descending ore so that the moisture is driven out of the ore by the time the ore reaches the bottom of the stack or chute. In the further descent of the ore from the stack or chute to the metal in the smelting zone between the electrodes, it is subjected to a preheating operation by heat communicated from the smelting zone and from the hot gases arising from the smelting zone so that the ore passes successively through a drying zone, a preheating zone and a smelting zone. The supporting means 11 and 12 normally support the ore so as to prevent the same from passing too rapidly to the crucible. When it is desired to draw off a molten charge, the supporting blades 12 are swung outwardly by operation of the handles 15 so that the ore is allowed to descend bodily into the crucible and displace the melted metal which rises over the lip 6 and is thereby discharged from the furnace. In some instances it may be desirable to allow the charge to remain in the crucible and cook after it is reduced to a melted state, and the retaining blades 12 are useful in this connection in holding the body of unmelted ore out of the crucible until it is desired to discharge the smelted metal. The furnace may be and preferably is used, however, as a continuous furnace, with a continuous feed and continuous discharge, and in that case the blades 12 may be moved partly or wholly to outermost position so as to allow a relatively free descent of the ore, or to. obstruct the ore sufiiciently to provide for the continuous motion required.

further object and use of, these blades and their operating arms is to provide for shaking or agitating the charge in case the charge should arch or hang up in the preheating and drying zones.

Oil or gas may be forced through pipe 27, into the molten iron, thereby adding carbon or other material where it is required, and also carrying the heat inward from the electrodes, so as to reduce their temperature several hundred degrees without loss or waste. In case a fuel gas is used, it takes up the oxygen contained in the magnetite, setting free the iron which is drawn off.

On account of the preheating of the ore by radiation and convection of heat from the smelting zone, comparatively little current is necessary to reduce the ore to molten iron after it reaches the smelting zone.

What I claim is:

1. In an electric furnace, the combination with a furnace crucible and a chute for supplying ore thereto, of means for obstructing the downward movement of the ore in the chute to relieve the molten matter in the crucible of its weight.

In an electric furnace, the combination with a furnace crucible and a chute for supplying ore thereto, of means for obstructing the downward movement of the ore in the chute to relieve the molten matter in the crucible of its weight, said obstructing means being movably mounted to enable it to be moved out of the way of the ore so as to permit the ore to descend into the crucible under the weight of the column of ore and to displace the melted metal in the crucible, said crucible having an overflow discharge opening over which the melted metal flows when so displaced.

3. An electric furnace having a chamber provided with electric heating means for producing a smelting zone, means for supplying a column of ore to said zone, a chamber surrounding said o're supply means and communicating at its lower end with the smelting zone and closed at its upper end for communicating the heat from the smelting zone to said column of ore so as to provide a drying zone for the incoming ore, and a preheating zone between the drying zone and the smelting zone.

4:. An electric furnace provided with eleo-1 tric heating means for producing a smelting zone, and a chute for feeding ore to said smelting zone, said furnace being provided with a chamber surrounding said chute and adapted to receive the heat from the smelting zone and communicate it to the orein the chute to heat and dry the same, said chamber being substantially closed at its upper end to retain the heat therein and communicating at its lower end with the smelting zone, said chute having perforations establishing communication between the inside of the chute and said chamber surrounding the chute.

5. An electrode for an electric furnace,

comprising a shell of wrought; iron and a core of copper.

6. An electrode for an electric furnace, comprising a shell of wrought iron and a core of copper cast into said shell.

7. An electrode and supply conductor for an electric furnace, comprising a wrought iron electrode shell, a Wrought iron conductor shell connected thereto, and a core of copper cast into said shells.

heating circuit member for an electric furnace, comprising a retaining inclosure of metal at high melting point and a core inclosed by said inclosure and consisting of a metal of better and of lower melting point than sald retaining inclosure.

9. A heating circuit member for an electric furnace, comprising iron piping having a portion forming a secondary coil of the transformer, a core of highly conducting metal cast into said piping, a primary coil, and a core of magnetic metal extending through the primary and secondary coils.

10. In an electric furnace, an electrode circuit forming a transformer secondary, a plurality of transformer cores extending through said secondary and arranged close together at the side wherb they pass through the secondary and diverging so as to be separated at their other sides, and a primary coil on each core at their separated sides.

In testimony whereof, I have hereunto set my hand at Vancouver, B. 0., this 30th day of August, 1913.

PARVIN WRIGHT. In presence of CHARLES STEWART,

ENNETT. 

